For example, a technique described in Japanese examined patent publication JP2003-71776 has been known as a technique for a leg type mobile robot, particularly the structure of a foot of the leg type mobile robot. A foot of the leg type walking robot described in JP2003-71776 connects with an end of the leg through an ankle joint, and is composed by a force sensor (floor reaction force detector) for detecting floor reaction force, a spring mechanism provided with a elastic member having an impact absorbing function, a foot sole frame, a foot sole plate and a sole sequentially from above.
The center of the ankle joint is offset (bias) backward and inward to the bottom surface, i.e. ground area, to be grounded on a floor surface.
Then, the floor reaction force detector is disposed so that the center of the floor reaction force detector agrees with the center of the ankle joint in a plane view (here, the center of the floor reaction force detector agrees to a sensitivity center of the Z-axis), and detects a floor reaction force entered from the ground area using a spring mechanism.
Thus, the influence of the impact at the time of landing is reduced using the spring mechanism object, while raising the detection accuracy of the floor reaction force by providing the floor reaction force detector to the foot near the ground area.
However, the leg type walking robot described in JP2003-71776 requires to enhance the speed (walk and run) of the travel. When the leg type walking robot moves at a high speed, large inertia force is generated on the leg. So as to reduce the inertia force, there is a desire to reduce the weight of the end side of the leg, that is, the weight of a foot. Especially, a downsizing and wait-saving of floor reaction force detector to be installed on the foot has been desired.
The present invention is made based on above described background, and aims to provide a leg type mobile robot, in which a downsizing and wait-saving of floor reaction force detector to be installed on the foot is enabled.
The leg type mobile robot of the present invention includes an body, legs each connected to the body via a first joint; and foots each connected to an end part of the leg via a second joint, wherein the foot includes at least one foot portion, which has a ground area to be grounded on a floor surface at the bottom thereof, and a floor reaction force detector for detecting floor reaction force acting from a floor surface through the foot portion, and wherein the center Pc of the second joint is offset against the position Pa in a plane view, the position Pa is the position where the distance to the remotest point of at least one ground area becomes minimum, and the center Pb of the floor reaction force detector is provided so that the center Pb is in the vicinity of the position Pa than the center Pc of the ankle joint in a plane view.
The position Pa can be put into the center of the circumscribed circle of minimum size of at least one of the ground area. According to this construction, the amplitude of the floor reaction force to be entered to the floor reaction force detector can be minimized that the case where the position of the center Pb of the floor reaction force detector is located at the same position as the center Pc of the second joint in a plane view.